The invention relates to suspensions for vans or semi-trailers and, more particularly, to a sliding frame under which the suspension that is mounted under. The sliding frame preferably has independent air-springs support towers, as well as cross-members which are preferably bolted in (and not welded), as well as oil-free shocks.
Pause can be taken to give the last option, the oil-free shocks, a little further introduction. It is one (among others) object of the invention to provide suspensions for vans or semi-trailers with a hydraulic-oil free (or substantially oil or grease free) shock absorber in use in replacement of the more conventional hydraulic oil shock, or petroleum-product lubricated shock. A further aspect of this relates to a ride air dampened, external air suspension damping system.
Air-spring equipped truck and trailer air-spring suspension systems use an air spring to carry vehicle load and provide suspension movement. But these suspensions still need a means to dampen the air spring so that the air suspension does not bounce due to a condition known as an “under-dampened” spring condition. To do this, suspensions use a shock absorber (damper). The main purpose of the shock absorber is to keep the suspension from bouncing so that the tire stays on the road for stability and for evening the tire wear.
Current truck and trailer air-spring suspensions are believed to use one or the other of two options to dampen the suspension.
Conventional means to dampen the air suspension include using an independently mounted hydraulic shock absorber in conjunction with the air spring. The shock absorber has internal fluid and orifices that work to dampen the bouncing movement of the air spring in both up (compression) and down (rebound) travel.
A recent introduction to the market employs an air spring that has—internal to itself, the air spring—means to dampen itself, in compression and rebound, so that an external hydraulic shock absorber is not needed for system operation.
It is an object of the invention to separate the two functions once again to two separate devices—spring in one device and damper in the other—while making the damper not only oil-free but also pneumatic. See U.S. Pat. No. 8,540,222—Westnedge et al. It is believed this offers better options for designing for capacity, for height variation options among (say) stepped-deck low ride to flat deck high ride, independent control over factors governing spring function versus factors governing damper function, and so on.
What is offered here is an improvement which overcomes the shortcomings of the prior art.
A number of additional features and objects will be apparent in connection with the following discussion of the preferred embodiments and examples with reference to the drawings.